Soldering of metallic articles, particularly soldering of electronic components to the surface of a metallic support, such as a printed circuitboard, is normally performed in industry according to two principal methods: wave soldering and reflow soldering.
The wave soldering method may also be used to plate metallic articles, particularly the metallic parts of electronic components.
To solder or plate a metallic article by the wave soldering method, the metallic parts of the said article that are to be wetted by the solder are generally fluxed by means of a flux. This latter is constituted of organic compounds, particularly organic acids and halogenated derivatives.
The fluxing has as an essential object to clean the metallic surfaces, principally to eliminate therefrom metallic oxides, so as to facilitate and improve the quality of their wetting by the solder.
After passage on the solder wave, flux residues remain on the treated metallic surfaces. These flux residues are corrosive and conductive, and must therefore be eliminated by a cleaning operation normally using halogenated solvents, in particular chlorofluorocarbons (CFC).
Reflow soldering consists of depositing a solder paste on localized receiving regions at the surface of a support, contacting metallic articles such as electronic components with the soldering paste, then heating the reflow solder paste, particularly by means of infrared radiation, by convection, in vapor phase, by a combination of infrared radiation and convection, for example in a reflow furnace.
The solder paste comprises a metal alloy powder dispersed in an organic medium comprising a flux. This flux is itself also conventionally constituted by organic acids and halogenated derivatives, and has the same function of cleaning metallic surfaces.
After heating the solder paste, here again flux residues persist on the surface of the support, which give rise to the same disadvantages as described above. As in the case of wave soldering, it requires eliminating these residues by a cleaning operation, generally using CFCs.